The field of the invention is surface deposition of transition metals.
Transition metals have several important uses in industry, such as components for metal alloys, electrical wiring and components, pipes, paint, industrial and automotive catalysts, and photographic paper.
It is important that the transition metal or metal alloy used is relatively pure with respect to the component metals, especially in electrical wiring and components. Therefore, it is imperative to control production of the desired transition metals and alloys such that contamination of the metals by impurities is held to a minimum.
It is equally important to produce the transition metal or metal alloy in sufficient quantities to make their use efficient and economical. Edwards et al. (Edwards) has described a method of making copper (I) formate, which can be used as a copper metal precursor, from anhydrous copper (II) formate. J.C.S. Dalton, p. 2463 (1973). However, the methods used by Edwards produce an insignificant amount of copper (I) formate formation (about 2%).
U.S. Pat. No. 5,094,686 issued to Kawakami et al. (March 1992) teaches that a fine copper powder can be formed through thermal decomposition of a copper complex. Kawakami, however, uses anhydrous copper formate and other anhydrous copper complexes as precursors to formation of copper powder. Kawakami limits the decomposition process to the solid phase of the copper complex precursor, and further limits the atmosphere of the decomposition process to be a non-oxidizing atmosphere.
U.S. Pat. No. 3,994,727 issued to Polichette et al. (Polichette) discloses a method of forming metal images using reducible metal salts and light sensitive reducing agents. There are two distinct layers on top of the substrate surface: a catalytic, non-conductive real image and an electrolessly deposited metal in the formation of the catalytic real image. Incorporated with the two distinct layers is an epoxy laminate that is designed to be an adhesive and a protectant. The laminate partially decomposes upon application of an energy source, but does not evaporate from the metal surface. Thus, the metal layer is contaminated with non-volatile decomposition products from the epoxy laminates.
Thus, there is still a need to efficiently produce metal complexes, pure metals and metal alloys in high concentrations without significant contamination.
The present invention provides methods and apparatus in which a metal precursor is formed in a process that includes the following steps: depositing a metal precursor on a substrate; adding an energy to reduce the metal precursor and to precipitate metal on the substrate as a continuous metal layer; and selecting the metal precursor and the energy such that the purity of the continuous metal layer is greater than 85%.
The present invention also provides methods and apparatus in which a metal is deposited onto a substrate by a process which includes the following steps: depositing the metal precursor onto the substrate in a desired pattern; and applying sufficient energy to decompose the precursor to precipitate metal in a continuous metal layer in the desired pattern.
Various objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the invention, along with the accompanying drawings in which like numerals, represent like components.